if only high stakes matches are counted than Shrapova vs Serena is 2-5, so don't start it

LOL don't get mad! Its true Nadia hasn't won a big match over Serena which is a basic criteria to be considered the rival/nemesis of a player. I don't think only big matches count but if a player can't beat someone at a slam or in the late rounds of any tournament they are hardly a nemesis.